As vocabulary grows…

As vocabulary grows…

…children vary immensely

with subgroups of variation



Vocabulary size
  • Girls > boys
    Eriksson et al, 2012; Frank et al, 2016
  • First-born > later-born
    Goldfield & Reznick, 1990
  • Higher SES > lower SES
    Arriaga et al 1998; Fernald, Marchman, & Weisleder, 2013


  • Quantity/quality of language input → vocabulary size
    Hart & Risley, 1995; Hoff, 2003
  • Vocabulary at 25 months → abilities at 8 years
    Marchman & Fernald, 2008


Do individual words carry demographic signal?

Data

Sex
– Assigned female at birth
– Assigned male at birth

Data

Birth order
First-born
Second-born
Third-born or later-born

Data

Maternal education
Below Secondary
Secondary (~high school degree)
College and Above (~college degree)

Analysis

For a language and demographic:

produces ~ age + birth_order + (age + birth_order | item)
  • fixed effect for each demographic in each language
  • random effect for each item for each demographic in each language
  • coding scheme gives difference between adjacent levels

Results

Results

Results

Results

Results

Results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Item results

Takeaways

  • Across languages, demographic factors have consistent direction but variable magnitude
  • Individual words are learned differentially by sex, birth order, maternal education
  • Avoid bias in test design by excluding demographically-linked items
  • Demographic differences in vocabulary size are influenced by specific content differences

Part of larger work on variability and consistency in language learning:
langcog.github.io/wordbank-book

All data and code available at: github.com/mikabr/item-demo